Friday, 19 April 2013

Project 5 : N4UJW Multiband longwire

I found this antenna some years ago and i always wanted to have a crack at building it once i had the time and materials. The design i followed is by N4UJW and can be found here :http://www.hamuniverse.com/shortwaveantenna.html
The original design required speaker line or even fencing wire as options. I went for plastic coated clothes line wire as i needed something more durable that would stand up to the winds we get here. So, 140 metres of line divided thus: 1st element: 43.891 meters (90 and 31 M bands), 2nd element: 36.149 meters (75 and 25 M bands), 3rd element: 28.011 meters (60 and 19 M bands) and 4th element: 24.171 meters (49 and 16 M bands).

original design

The mounting was fairly straight forward with the exception of the insulators/spacers that i just could not get to function correctly. As stated in the image, the premiss is that each element will support the one above. In practice, no matter what material i made them from (including bamboo), they offered no support. In the end i reverted to tying each element individually to the support mast.

Mounted on the mast, showing the co-ax/element harness

I have been testing this antenna for a couple of days now and it beats my old faithful longwire hands down. It is used in conjunction with my homebrew pre-selector (see previous project) and a 9 volt, single transistor RF signal booster circuit i built. This antenna is perfect for the utility monitoring and signal decoding i do with my SDR and programs. Build time was a couple of days.....on and off.